Synergy, several ad networks have fallen by the wayside during the past few months.
AdClub.net, SafeAds, CNET's Gamers Alliance, ClearBlueMedia, UGO, Snowball and several others have either shut up shop completely, or severely pruned their programs. Others, such as ClickAgents, Flycast and WebsiteSponsors have been merged or acquired by larger media companies in order to strengthen their position in the market, and to eliminate competition.
As you are most probably aware, the sharp drop-off in ad rates is directly related to the tech crash, which sent many big-spending online companies out of business. Of course, the slowing economy hasn't helped, either. Traditional advertisers have continued to state that they will increase their online ad budgets over the coming few years, though, so web publishers are forced to play the waiting game.
I don't think that banner ad rates will reach the heights that we saw during late 98-99, but they will certainly bounce back from their present lows by the second half of 2001.